A medication delivery device may comprise a housing containing a cartridge which contains medication. A membrane may be located at the distal end of the cartridge and a bung may be located at the proximal end of the cartridge. A delivery needle assembly, which comprises a needle, may be attached to the housing so that the needle punctures the membrane. The medication can be expelled through a needle of the delivery needle assembly. A drive mechanism of the medication delivery device is configured to push the bung along the cartridge so that the medication is expelled through the needle. The delivery needle assembly is suitable to administer the medication to a patient.
The drive mechanism may comprise a piston which pushes the bung to the distal direction. When a predetermined dose of medication is delivered, the piston moves in the distal direction, wherein the piston moves forward a distance which corresponds to the predetermined dose value. The bung should move forward the same distance to ensure that the predetermined dose value is delivered. However, the piston may not lie against the bung before first use. In this case the distance of the piston would not correspond with the distance of the bung, so that a wrong dose would be delivered. First use means use of the medication delivery device to administer a first dose from the cartridge to the patient.
Prior to first use of the medication delivery device, the user should prime the medication delivery device. Priming means that a priming dose is delivered before first use. The priming dose is not injected to the patient. The priming dose value may be less than a dose value which is injected to the patient. After priming the piston lies against the bung, so that the correct to dose can be delivered.
Some users fail to prime the medication delivery device before use. It is an aim of the invention to provide means for overcoming this.